Convolved transmission line



April 11, 0 N. E. LINDENBLAD 2,503,955

CONVOLVED TRANSMISSION LINE Filed Sept. 24, 1942 2 Sheets-Sheet l INVENTORI zvguaLauzelazaz 7%? K ATTORN EY Ap 11, 1950 i N. E. LINDENBLAD 12,503,955

I CONVOLVED TRANSMISSION LINE Filed Sept: 24, 1942 2 Sheets-Sheet 2 INVENTOR may erzfiiad BY lg/2M ATTORN EY Patented Apr. 11, 1950 UNITED STATES PATENT OFFICE convorvan TRANSMISSION LINE Nils E. Lindenblad, Rocky Point, N. Y., assi'gnor to Radio Corporation of of Delaware America, a corporation Application September 24', 1942, Serial No. 459,497

i the provision of an artificial line having characteristics which do not vary with changes in the frequency of energy applied thereto.

A further object of the present invention is the provision of an artificial line which has a phase shift characteristic which is linear with respect to frequency.

j Still a further object of the present invention H is the provision of a compact artificial line which,

in spite of its size, will handle large amounts of .i

energy.

The foregoing objects, and others which may appear from the following detailed description, are attained in accordance with the principles of the present invention by so convolving coiling or folding a natural line that it occupies a small space without at the same time introducing such mutual inductive effects, either electrostatic or 1 Claim. (Cl. 17844) 1 ing [4 whichis hermetically sealed at each end by end plates [6 and I1. Tube may be supported in position within casing l4 by being rigidly attached at one end to plate l6. At the other end tube [0 passes through a supporting plate l which is secured within casing M. The ends of the line Hare-connected to terminals I8 and [9 carried by insulator bushings and 2| secured in a side wall of casing l4; End plate I1 is preferably provided with a pressure gauge 22 and an t inlet valve 24 by meansof which a predetermined electromagnetic, between different convolutions or layers of the coiled line that it ceases to act as a natural line. It is to be understood that in convolving the conductor of the end line, the line may be wound or twisted either upon itself or wrapped about another object, or it may be folded back and forth on itself or with relation to another object.

The present invention will be more fully understoodby reference to the following detailed description, which is accompanied by a drawing in which Figure 1 illustrates an embodiment of the invention, while Figures 2 and 3 illustrate a portion of the modification thereof in front and side views, while Figures 4 and 5 illustrate in elevation, partly in section, and in plan, a further modification of the invention and Figures 6 and 7 illustrate further modifications of the invention.

Referring, now, to Figure 1, reference numeral It indicates a conductive tube carrying a plurality of insulating rods ll around the outside of the tube. The purpose of insulating rods H is to act as a spacing support for coiled line [2 which is space wound about the outside of the rods. The coiled line l2, together with the supporting tube I0, is supported within an outer metal caspressure of gas maybe maintained within the casing l4. Tube H)- fits within the central aperture in plate [5 loosely enough that the gas within the casing may flow by the plate. Apertures such as at l5 may be provided in the plate if it is deemed necessary. Due to the comparatively small spacing of the convolutions of line [2 from the supporting tube I0 and the outer casing 14, the mutual effects between adjacent turns or convolutions of coil [2 are so reduced that the line acts substantially the same as though it were straight instead of being coiled up.

The modification shown in Figures 2 and 3 utilizes a plurality of metal plates 26, 21 and 28, the coiled line conductor l2 being supported by plate 21 and surrounded by plates 26 and 28 whereby the adjacent portions are shielded one from the other. The central plate 21 carries on opposite edges insulating support strips 30 and 3| upon which the convolutions of coil l2 are wound. The plates are maintained in a parallel relationship by suitably arranged bolts 25 and spacers 25'. Due to the close spacing of the successive convolutions of coil l2 from the metal plates 26, 21 and 28, the mutual effects therebetween are so reduced that the line acts as though it were a straight line.

The requisite number of units as shown in Figures 2 and 3 to obtain a desired line length may be connected in series and placed in a liquid tight casing filled with transformer oil. Thus the current carrying capacity of the line is somewhat improved due to better cooling and, also, the successive convolutions of the line are additionally insulated one from the other.

The further modifications shown in Figures 4 and 5, like that of Figures 2 and 3, utilizes a plurality of separate line sections each of which may be supported within a shield 32. The sections are connected in series and placed withina conductive container 34 which is filled with transformer oil. The container may be covered by an insulating top 35 which carries a terminal 36 to which one end of the line is connected, the

3 other end being connected to the container 34. Each line section, in this modification, is constructed by first winding the conductor upon a small diameter mandrel to form an elongated helix, the successive turns of the helix being slightly spaced one from the other. The helix, after being removed from the mandrel is then space wound upon-an insulating support 31-which may be a glass tube orirod. *ilhessupport 31 may be threaded to hold the turns in place or they may be cemented to the support by coating them with shellac or other cement. The shields 32 are preferably welded or soldered "together into "a honeycomb-like arrangement with combined spacing fins and supporting legs .38 attached to the periphery to maintain the desired relationship between the shields, the casing andvthe coils.

The further modification'of the present invention shown in Figures 6 and 7 is of particular advantage when artificial lines of low characteristic impedance are desired. In the exploded riewaof Figure-6 vis shownthe conductor 42 in the .form of'a long flatzribbonfolded back and forth .in a zigezag manner. On each side of the ribbon 42 is placed :a long imulating strip 43.

-If -des-ined, the ribbon :may be wound with in- :sulating material indzhe same :way as magnet wire insulated, on an insulatingsleeving woven over Bthe ribbon. It is so shown in Figure 7. Into each' of the bends of the zig-zag ribbon is .inserted a metallicjgroundplate i! similar in form -:to that. showninFigure 2 inplan. Theeround- -:ed,plates A! are then, pressedclosely together and :secured innpositionby meansicf securing bolts 25.

While I have, particularly shownanddescribed :several modifications-of the present invention,.it should be clearly understood tlratzthe invention is 1101; limitedl'to theseforms alone, but thatmodifications maybeimade.

I claim:

An artificial line including an elongated inner conductive tube, a plurality of thin insulating strips arranged about said conductive tube parallel to the axis of said tube and an elongated conductor Wound in a spaced relationship over said insulating strips, an outer conductive tube close- .ly surrounding said inner conductive :tube and spacing between said conductive tubes and said conductor being small substantially to decouple successive turns of the winding of said conductor "one from the other, said outer conductive tube being sealed fiuidztight, and means for main- :taining aniinsulating fluid under pressure within said outer conductive tube, the spacing between said conductive tubes being maintained by annular discs interposed between said tubes at .eachiend of the winding on said inner conductive tube.

NILS .E. .LINDENBLAD.

REF ER'EN'CES :CITED Thefollowing references are of record in the file of this patent;

UNITED STATES "PATENTS Number -Name Date "792248 Campbell's 'June 13, 1905 1,893,618 Forbes Jan. 10,193 1,904,199 Brewer :Apr. .18, 1933 11,957,481 W-illoughby .May 8, 1934 2,014,004 Mershon ....-Sept. 10, 1935 2,111,381 Barton- Mar.' ;15, .1938 2,124,029 Gor'iklin et al. July/19,1938 2,149,336 Darnell Marj I, .1939 2,158,493 Brails'ford et a1. "May 16, 1939 2,227,846 Rust -Jan.'7, 1941 "2,232,042 Alford Feb. '18, "1941 2,258,261 Roosenstein 'Oct.'7,"1941 

